From 230 V
AC a DC supply of + 5 V is obtained. The power supply is given to
the other blocks. The pulse generator at a particular frequency
generates the clock pulses. The clock pulses are counted by a
counter and gives output after every 10 pulses. The counter drives
the transistors, which form the triac firing circuit. The
transistors fire the triacs and they provide sufficient current to
the load. Decorative bulbs are connected as load for each triac.
The bulbs are sequentially turned ON and OFF in forward and
reverse way.

The IC 555
works as the pulse generator and feeds the clock pulses to IC
4017. IC 4017 is the heart of this circuit. It works as a counter
and gives the output after every 10 pulses. It drives the
transistors, which in turn fire the triacs. The triac provides
sufficient current to the load.